Blowout preventers are used to maintain control of wells during drilling. Ram-type blowout preventers are used to close on the drill or pipe string to contain pressure in the well. At times it is necessary to strip the string through the closed rams. This stripping movement can severely wear or abrade the face of the resilient packer. Another reason that the packers of ram-type blowout preventers are subject to wear is that to provide a seal they must move into tight engagement with the irregular surface of the string when closed and such ability causes the packers to be subject to extrusion. The design of ram packers is thus a compromise to provide the needed feed or available movement of the material with the maximum abrasion and extrusion resistance.
Examples of prior ram-type blowout preventers can be seen in U.S. Pat. Nos. 2,883,141 and 3,692,316 which also disclose the use of upper and lower packer plates designed to minimize extrusion damage. Knitted wire mesh or braided wire in the packing immediately adjacent the face of the wear plates have been used in an attempt to limit extrusion of the packing. U.S. Pat. Nos 4,219,204 suggests the use of such knitted wire in a seal as an anti-extrusion means. Also, it has been known to embed a canvas fabric in seals, such as mud pump piston seal rings, to provide extended seal life.